Interlocking relay



Sept. 24, 1935. P N MART N 2,015,348

INTERLOCKING RELAY Filed Dec. so, 1955 4 Shee ts-Sheet l INVENTOR Z M/Vamm W H15 AITORNEY Sept 24, 1935. p N -rm 2,015,348

INTERLOCKING RELAY Filed Dec. 30, 1935 4 Sheets-Sheet 9 INVENTOR Paul M Martin .32 BY Q QW H [S A TTORNEY Sept. 24, 1935. P. N. MARTIN INTERLOCKING RELAY Filed Dec. 30, 1933 4 Sheets-Sheet 3 [NV gVTOR Paul IVY/461F512 BY 4am HIS ATTORNEY Swt 24 1935. P, N. MARTIN INTERLOCKING RELAY Filed Dec. 30, 1935 4 Sheets-Sheet 4 INVENTQR Paul N Mamm BY Q31 HIS ATTORNEY Patented Sept. 24, 1935 UNITED STATES PATENT OFFICE INTERLOCKING RELAY Application December 30, 1933, Serial No. 704,650

19 Claims.

My invention relates to interlocking relays, and particularly to interlocking relays in which two armatures controlled by separate electromagnets are interconnected by mechanical means in such manner that when one armature moves away from its associated electromagnet, subsequent movement of the other armature away from its associated electromagnet is restricted.

Specifically, my present invention relates to improvements in interlockin relays of the type described and claimed in Letters Patent of the United States No. 1,799,629 granted to William K. Lockhart and Thomas J. OMeara, on April 7, 1931, and also to improvements in interlocking relays of the type described and claimed in Letters Patent of the United States No. 799,452 granted to W. W. Coleman on September 12, 1905.

I will describe three forms of relays embodying my invention, and will then point out the novel features thereof in claims.

In the accompanying drawings, Fig. l is a View showing in front elevation one form of interlocking relay embodying my invention. Fig. 2 is a sectional view of the relay shown in Fig. 1 taken on the line II-II of Fig. 1. Fig. 3 is an isometric view of a portion of the relay shown in Figs. 1. and 2. Fig. 4 is a View similar to Fig. 3 but showing a modified form of the relay illustrated in Figs. 1. and 2. Fig. 5 is a side elevational view showing another form of interlocking relay also embodying my invention. Fig. 6 is a detail view of a portion of the interlocking mechanism of the relay shown in Fig. 5.

Similar reference characters refer to similar parts in each of the several views.

Referring first to Figs. 1 and 2, the relay, in the form here shown, comprises two similar electromagnets A and B mounted end to end on a top plate C of insulating material. The cores of the electromagnet A are connected together at their upper ends in the usual manner by a backstrap i and terminate at their lower ends in enlarged pole pieces .2 located beneath the top plate C, while the cores of the electromagnet B are similarly connected together at their upper ends by a back-strap 5 and terminate at their lower ends in enlarged pole pieces 2 also located beneath the top plate C.

The electromagnet A controls an armature 5 pivotally supported on pivot pins 4 carried by the downwardly extending lugs of a bracket 3 fastened to the sides of the pole pieces 2 Attached to the underside of the armature 55 by means of insulating supports l (see Fig. 2) are contact fingers 8 here shown as two in numher. When the electromagnet A is energized, the armature 5 is drawn upwardly against nonmagnetizable stops 6 and the contact fingers i then each engage a front contact .l fastened by means of a holder (9 to a terminal post H carried by the top plate C. When electromagnet A is deenergized, however, the armature E5 drops downwardly under the influence of gravity, and except under conditions which will be explained hereinafter, the contact fingers 8 then each engage a back contact I2 attached to a terminal post 13 carried by the top plate C. In similar manner, the electromagnet 13 controls an armature 5 pivotally supported on pivot pins 4 carried by the downwardly extending lugs of a bracket 3 fastened to the sides of the pole pieces 2* Contact fingers 8 are attached to the underside of the armature 5* by supports which are not shown in the drawing, but which are similar to the support-I shown in Fig. 2. The contact fingers 8 coact with front contacts 9 and back contacts H in the same manner that the contact fingers 8 coact with the front contacts 9 and the back contacts I 2 as will readily be understood from an inspection of the drawings.

Also attached to the armatures 5 and 5*, respectively, are two interlocking arms M and M which cooperate with two locking dogs [5 and I6 for at times restricting downward movements of the armatures. The locking dogs l5 and 16 are pivoted on a horizontal shaft ll carried by a yoke I8 attached to the top plate C by screws Hi, the dogs being held in proper spaced relation on the shaft I! by separators 29. The dog I5 is provided with a vertical arm w and with a horizontal arm l5 and is biased, by means of a counterweight 2| attached to one end of the horizontal arm I5 to an inoperative position in which the vertical arm I5 engages a stop rod 22 carried by the yoke I8. The end of the horizontal arm l5 opposite to the counter-- weight 2| projects under, and cooperates with a resilient strip 23 secured to the interlocking arm I 4 The strip 23 is so disposed that when the armature 5 is released and drops, this strip will move into engagement with the horizontal arm l5 shortly after the armature passes mid stroke and will, during the remainder of the downward stroke of the armature, rotate the dog it to an operative position which will be described more fully hereinafter. The dog i5 is very light in weight and is loosely pivoted on the shaft i! so that the force required to drive this dog is small; and the strip 23 is made just stiff enough to drive the dog with only a slight deflection of the strip. A backstop 26 of rigid material is secured to the arm M below the strip 23 and cooper-ates with the strip 23 to determine accurately the position at which this strip will engage the dog [5 during the downward stroke of the armature 5 Furthermore, a-top stop 21 of rigid material is also secured to the arm M above the strip 2" and is provided with a certain amount of clearance between its outer end and the strip, so that if some unusual resistance to the movement of the dog [5 should develop which would cause abnormal deflection of the strip 23* the step will engage the strip and will limit the amount? of deflection of the strip, thus insuring that the dog will still be driven to its operative position in response to downward movement of the armature 5.

When the dog !5 occupies its operative position, the upper end of the vertical arm [5 lies in the path of the downward movement of an offset portion 2B forming part of the interlocking arm M but when the dog occupies its inoperative position, the vertical arm IE is then out of the path of movement of the oiiset portion 28. It follows that if armature 5 is released and drops when the dog I5 occupies its inoperative position, the armature 5 will move to its lowermost position, but that, if the armature 5 is released and drops when the dog l5 occupies its operative position, the downward movement of this armature will be limited by engagement of the offset portion 28 with the upper end of the vertical arm Hi. The parts are so proportioned that when the oflfset portion 28 engages the vertical arm l5, the armature 5 will be held at approximately mid stroke and both the front and back contacts controlled by this armature will then be open.

A retaining spring 29 is secured at one end to the upper side of the interlocking arm I4, and the other end of this spring projects beyond the outer end of the offset portion 28 and is provided with a depending tip 30 which, when the dog I5 occupies its operative position and the armature 5 is released, extends downwardly past the left-hand side of the Vertical arm l5 of the dog 15 as viewed in Fig. 2 in such manner that there is some clearance between the tip 30 and the left-hand side of the dog, but that this clearance is not enough to permit the dog to move out from under the offset portion 23 and allow the armature 5 to drop to its lowermost position. It follows that, when the dog i5 has moved to its operative position and the armatiue 5 has dropped to the position in which the offset portion it the vertical arm of the dog l5, no amount of vibration will cause the dog l5 to release the armature 5 and permit it to drop to its lowermost position in which the back contacts controlled thereby are closed.

With the dog it and cooperating parts of the two interlocking arms constructed in the manner thus far described, the sole force acting to return the dog l5 to its inoperative position after the dog has once been moved to its operative position is the counterweight 2 I. It is desirable that this counterweight should be as light as possible because the lighter this counterweight is made, the less the force required to drive the dog 15 will be, and hence the greater the contact pressure of the back contacts controlled by the armature 5 will be. When the counterweight 2! is made light in weight, however, if any abnormal resistance to the movement of the dog 25 should develop, the dog after being moved to its opera- In its cured to the interlocking arm it below the 1' 23 and the outer or free end of which projects beneath the horizontal arr-n E 3 o the interlocking arm 85. The strip 3i so di when the armature 5 is in the do i5 oc a strip will lo zontal arm ifi oi the dog. It will be apparc. therefore, that if the dog occupies is operative position when the armature i picks up, the strip 3P will move into engagement v n horizontal arm iii of the dog iii, and will exert a force on the dog 55 which tends to 1'ot ,ti dog the same direction. as the force due to the counterweight E 9, thus tending to restore 1.1%) deg ii inoper 2 position. The parts are so proportioned that the counterweight 25 is just heavy enough to hold the dog it in its inoperative p tion after it has once been moved to inoperetive position, and that the total force exerted b the strip and counterweight is just sufiicient insure the proper return of the dog to its in irative position when the armatures *5 and both picked up following the previous re these armatures, and will not in any or .1 sufficient to cause the vertical arm iii of the do u e of iii to move out of engagement with th oflse portion 28 of the interlocking arm w electromagnet A is deenergised. .[L d stop 32* may be pro-vided above the strip prevent vibration or change in adjusti: the strip.

An alternate arrangement which may be provided to return the dog E5 to its inoperative position when the armatures 5 both become picked up following the movement of the dog 5 to its operative position due to the dropping of the armature 5 is shown in Fig. 4. As here illustrated, the flexible strip Bi shown in Figs. 1 to 3 has been replaced by a rigid strip 33* so arranged that When the armature 5 picks up, if the dog E5 then occupies its operative position, the strip 33 will move the dog l5 from its operative position to substantially the position in which the left-hand side of the vertical arm iii of the dog it engages the depending tip 3E of the retaining spring I have found that any tendency of the dog iii to stick in its operative position will usually occur when the vertical arm l5 of the dog ii": is engaging the stop rod 25, and that when the dog is moved away from the position in which it engages the stop rod by the rigid strip 33 in the manncr just described, this tendency is overcome. The movement of the dog by the rigid stop while the armature 5 is held in its mid stroke position Z of the these conditions between the left-hand side of the 75 vertical arm l5 and the depending tip on the retaining spring. I

The dog I6 is similar to the dog l5, and cooperates with parts of the two interlocking arms M and M which are similar to the previously described parts with which the dog |5 cooperates, to limit the downward movement of the armature 5 when the electromagnet B becomes deenergized following the deenergization of the electromagnet A. The parts of the interlocking arms M and M with which the dog l6 cooperates have, in most instances, been designated by the same reference numerals as the corresponding parts with which the dog |5 cooperates, but with suitable distinguishing exponents added, and it is believed, therefore, that the construction and operation of the dog l6 and associated parts of the interlocking arms will be readily understood from the foregoing and from an inspection of the drawing without further description. If a fuller description of the dog I6 and cooperating parts and of the operation of the relay proper as a whole is desired, reference may be had to the previously referred to patent to Lockhart and OMeara No. 1,799,629.

It should be particularly pointed out that with an interlocking relay constructed in the manner described, the locking dogs are positively driven in both directions, thus insuring their proper operation.

Referring now to Figs. 5 and 6, I have here shown another form of interlocking relay which also embodies my invention. This relay comprises two electromagnets A and B mounted transversely on an insulating top plate adjacent the opposite ends of the top plate. The electromagnets A and B are similar in all respects to the electromagnets A and B shown in Fig. 1, and each controls an armature, designated by the reference character 35 with a suitable distinguishing exponent, in the same manner that the electromagnets A and B control the associated armatures and 5*. Attached to the underside of each armature 35 by means of insulating studs 36 are a plurality of contact fingers 31 only two of which are visible in the drawing, the remaining contact fingers being behind those shown. Each contact finger 31 is connected by means of a flexible connector 33 with a terminal post 39 mounted on the top plate 0 and each contact finger carries a contact spring 40 which, when the associated armature is picked up, engages a contact block 4| secured to a terminalpost 42 mounted on the top plate C to close a front contact 4ll4 Each contact finger 31 also carries a contact spring 43 which, when the associated armature is released and drops to its lowermost position, engages a contact member 44 attached to a contact support 45 fastened to a terminal post mounted on the top plate C behind the adjacent terminal post i2, thereby closing a contact 4344.

The interlocking mechanism of the relay comprises two interlocking arms Mi and 49, the one of which, 46 is attached at one end to the armature 35 and the other of which, 46 is attached at one end to the armature 35 The two interlocking arms 46* and 46 extend toward each other and each divides at its outer end into upper and lower bifurcations, the upper bifurcations being designated by the reference characters 47 and fiil respectively, and the lower bifurcations being designated by the reference characters 18 and Q8 respectively.

The interlocking mechanism also comprises a locking dog 49 which is pivotally supported adand 48*; ,with two notches 55 and 55 which.

cooperate with depending tips 56 and 56 provided on retaining springs 59 and 59 secured to the interlocking arms 46 and 46 and with two depending stops 58 and 60 which cooperate with the opposite sides of the lower part of the bracket 5| to limit the rotation of the dog. A laterally projecting pin 58 is secured to the dog 49 adjacent the lower end of the dog, and this pin cooperates with the depending legs M and 6| of a U-shaped spring 6| in such manner that the dog 49 is biased by the spring 6| to a vertical position in which it is shown in the drawing. The spring 6| is secured to the bracket 5| by means of one of the bolts 52 which secures the bracket to the top plate C.

The interlocking mechanism further comprises .tWo resilient strips 62 and 82 embodying my present invention. The strip 62* is secured at one end to the interlocking arm 46 by means of the same bracket which fastens the retaining spring 59 to this interlocking arm, and the free end of this strip extends toward the dog 49 and cooperates with the underside of the operating arm 53* of this dog. The strip 62 is secured at one end to the interlocking arm 46 in the same manner that the strip 62 is secured to the interlocking arm 46*, and cooperates at its free end with the underside of the operating arm 53 of the locking dog. The strips $2 and 62 are so adjusted that when the dog 49 occupies its vertical position and the armatures 35 and 35* are both picked up and closed against their stop pins, these strips will just clear the associated arms, but that, if the dog d9 is displaced from its vertical position in a counter-clockwise direction when the armature 35 is picked up, the arm 53 of the dog will engage the strip and deflect it downwardly, and that, if the dog 49 is displaced from its vertical position in a clockwise direction while the armature 35 is picked up, the arm 53 will engage the strip 62 and deflect it down wardly. It follows, therefore, that when the armatures 35 and 35* are both picked up, the dog 49 is biased to its vertical position by the springs 62, but since these springs are both out of engagement with the dog, no force is exerted on the armatures 35 and 35 by the springs in their upper positions. If desired, top stops 63 and 63 may be secured to the interlocking arms 66 and 46 above the strips 62 and 52 to accurately position the strips with respect to the arms in order to insure the desired cooperation between the strips and the dog.

In explaining the operation of the relay shown in Figs. 5 and 6 as a whole, I will assume that magnets A and B are both energized, so that the armatures 35 and 35 are both picked up as shown in the drawing, and that magnet A becomes deenergized sometime prior to the deenergization of magnet B and again becomes energized prior to the energization of magnet B Under these conditions, when magnet A becomes deenergized, armature 35 will drop to its lowermost position, and this movement of the armature will cause bifurcation l! of interlocking arm 45 to move into engagement with the operating arm 53 of dog 49 and rotate this dog in a counter-clockwise direction to an extreme position in which the stop 6i) engages the frame 5|. When dog 49 occupies this extreme position, the holding projection 54 is disposed in the path of movement of the bifurcation 48 of the interlocking arm 46 and the notch 55 is disposed in the path of movement of the tip 56 of the retaining spring 59 As a result, when the magnot B subsequently becomes deenergized and releases the armature 35 the bifurcation 48 will move into engagement with the shoulder 54 and will thus prevent the armature 35 from dropping past lnld stroke position, and the tip 56 of the retaining spring 59 will enter the notch 55 in the dog 39 and will thus insure that this dog will remain in its counter clockwise extreme position as long as magnet B remains deenergized. When armature 35 occupies its mid stroke position, both the front and back contacts controlled by this arinature are open. When magnet A again becomes energized, armature 35 will pick up, thereby causing bifurcation 41 to move out of engagement with the operating arm 53 of dog 69 and strip 62 to move into engagement with the arm 53 The movement of the bifurcation il out of engagement with the arm 53 of dog 4% removes the force exerted on the dog by the armature 35 tending to hold the dog in its counter-clockwise extreme position, and the movement of the spring 62 into engagement with the arm 53 of the dog 49 causes a force to be exerted on the dog which aids that exerted on the dog by the spring Bi tending to restore the dog to its vertical position. The dog 49, however, is held in its counter-clockwise extreme position by the engagement of the tip 56 of the spring 59 with the notch 55 and also by the engagement of the inclined upper surface of the shoulder 54 with the similarly inclined under surface of the bifurcation 48 until magnet B again becomes energized, at which time the resultant picking up of armatures 35 withdraws the tip 56 of spring 59" from engagement with the notch 55 and moves the bifurcation 4? out of engagement with the shoulder 54*, thus permitting the dog to return to its vertical position. When the dog reaches its vertical position, all parts are restored to their normal positions in which they are shown in the drawings.

A sequence of operation similar to that just described occurs when magnet B becomes deenergized before magnet A and is again reenergized prior to the reenergization of magnet A the dog 49 under these conditions being rotated in a clockwise direction by the dropping of the armature 35' to the extreme position in which the stop GD engages the bracket 5i, and acting when rotated to this extreme position to prevent the armature 35 from dropping past its mid stroke position, the dog subsequently being restored to its mid stroke position by the combined action of the spring 6i and the strip 52 when both armatures 35 and 35 are restored to their picked up positions due to the reenergization of the magnets A and B It will be seen, therefore, that with the relay constructed as shown in Figs. 5 and G, the dropping of either armature rotates the dog 39 to an extreme position in which it prevents the other armature from dropping far enough to close the back contacts controlled by such other armature, and that when both armatures are subsequently picked up, the

dog is restored to its normal position by the combined action of the spring El and one or the other of the strips 62, depending upon which armature is the last to be picked up.

One advantage of providing the strips (52 and 62" to aid in restoring the dog "iii to its mid stroke position following the releasing and subsequent picking up of both armatures 35 in the manner described rather than securing the same restoring force by increasing the biasing force exerted on the dog by the spring BI is that the use of the strips 52 does not increase the force which the armatures must exert on the dog to move it from its normal position to its operative position, whereas, if the biasing force exerted on the dog by the spring iii were increased, the force which the armatures would then have to exert on the dog to drive it to its operative positions would be increased. Any force which the armatures must exert on the dog to drive it to its operative positions decreases the contact pressure exerted on the back contacts controlled by the armatures a corresponding amount since the weight of the armatures is the only force available both for driving the dogs and for closing the back contacts and desirable for obvious reasons that the back contact pressure of a relay of the type derib-ed should be as great as possible.

The application of interlocking relays of the type described to the control of highway crossing signals and other similar railway signaling devices is well known and need not be described herein.

Although I have herein shown and described only three forms of interlocking relays embodying my invention, it is understood that various ch nges modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. An interlocking relay comprising two electro-magnets, two armatures one controlled by each electrcmagnet, a movable locking dog, means r attached to one armature for at times moving said dog from a first position to a second position for at other times partly returning said dog to its first position, and means attached to the other armature and cooperating with said dog for first position, and rigid means attached to the other armature and cooperating with said dog for restricting the movement of said other armature when said dog occupies its second position.

3. An interlocking relay comprising two electromagnets, two armatures one controlled by each electromagnet, two movable locking dogs, means attached to one said armature for at times moving one of said dogs from a first position. to a second position and for at other times partly restoring said one dog to its first position, means attached to the other armature for at times moving the other dog from a first position to a second position and for at other times partly restoring said other dog to its first position, and still other means separately controlled by said Til armatures and separately coacting with said dogs for restricting the movement of the associated armature when the dog controlled by the other armature occupies its second position.

4. An interlocking relay comprising two electromagnets, two armatures one controlled by each electromagnet, two movable locking dogs, resilient means attached to one said armature for at times moving one of said dogs from a first position to a second position and for at other times exerting a force on said one dog which tends to restore it to its first position, resilient means attached to the other armature for at times moving the other dog from a first position to a second position and for at other times exerting a force on said other dog which tends to restore it to its first position, and rigid means separately controlled by said armatures and separately coacting with said dogs for restricting the movement of the associated armature when the dog controlled by the other armature occupies its second position.

5. An interlocking relay comprising two electromagnets, two armatures one movable toward and away from each electromagnet according as such electromagnet is energized or deenergized, two movable dogs, a first resilient member attached to one said armature and cooperating with one said dog in such manner that when said one armature moves away from its associated electromagnet a force is exerted on said one dog which tends to rotate said one dog from a first position to a second position, a second resilient member attached to said one armature and cooperating with said one dog in such manner that when said one armature moves toward its associated electromagnet a force is exerted on said one dog which tends to rotate said one dog from its second position to its first position, a third resilient member attached to the other armature and cooperating with the other dog in such manner that when said other armature moves away from its associated electromagnet a force is exerted on said other dog which tends to rotate said other dog from a first position to a second position, a fourth resilient member attached to said other armature and cooperating with said other dog in such manner that when said other armature moves toward its associated electromagnet a force is exerted on said other dog which tends to rotate said other dog from its second position to its first position, and rigid means separately controlled by said armatures and separately coacting with said dogs for restricting the movement of the associated armature when the dog controlled by the other armature occupies its second position.

6. An interlocking relay comprising two electromagnets, two armatures one movable toward and away from each electromagnet according as such electromagnet is energized or deenergized, two movable dogs, a first resilient member attached to one armature and cooperating with one said dog in such manner that when said one armature moves away from its associated electromagnet a force is exerted on said one dog which tends to rotate said one dog from a first position to a second position, a second resilient member attached to said one armature and cooperating with said one dog in such manner that when said one armature moves toward its associated electromagnet a force is exerted on said one dog which tends to rotate said one dog from its secend position to its first position, a third resilient member attached to the other armature and co operating with the other dog in such manner that when said other armature moves away from its associated electromagnet a force is exerted on said other dog which tends to rotate said other dog from a first position to a second position, a fourth resilient member attached to said other armature and cooperating with said other dog in such manner that when said other armature moves toward its associated electromagnet a force is exerted on said other dog which tends to rotate said other dog from its second position to its first position, and rigid means separately controlled by said armatures and separately cooperating with said dogs for restricting the movement of the associated armature away from its associated electromagnet when and only when the other armature has previously moved away from its associated electromagnet.

7. An interlocking relay comprising two electromagnets, two armatures one controlled by each electromagnet, a pivoted locking dog provided with a vertical arm and a horizontal arm and with a counterweight secured to one end of the horizontal arm, two resilientstrips secured to one said armature and coacting with the horizontal arm of said dog at the end opposite to said counterweight for rotating said dog between two positions, and a rigid member attached to the other armature and provided with means for engaging said vertical arm when said dog occupies the one of its two positions to limit the movement of the other said armature.

8. An interlocking relay comprising two electromagnets, two armatures one controlled by each electromagnet, a pivoted locking dog provided with a vertical arm and a horizontal arm, two resilient strips secured to one said armature and coacting with the horizontal arm of said dog for rotating said dog between two positions, and a rigid member attached to the other armature and provided with means for engaging said vertical arm when said dog occupies one of its two positions to limit the movement of the other said armature.

9. An interlocking relay comprising two electromagnets, two armatures one controlled by each electromagnet, a pivoted locking dog having a horizontal arm and a vertical arm and movable between an operative and an inoperative position, a counterweight secured to one end of the horizontal arm of said dog for biasing said dog to its inoperative position, a first resilient strip attached to one said armature and coacting with the horizontal arm of said dog at the end opposite said counterweight for at times moving said dog from its inoperative to its operative position. in response to the movement of said one armature away from its associated electromagnet, an interlocking arm attached to the other said armature and provided with an oifset portion for engaging said vertical arm when said dog occupies its operative position to limit the movement of said other armature away from its associated electromagnet, and a second resilient strip secured to said one armature and cooperating with the horizontal arm of said dog at the end opposite said counterweight for at times exerting a force on said dog when said one armature is moved toward its associated electromagnet to assist said counterweight in restoring said dog to its inoperative position.

10. An interlocking relay comprising two electromagnets, two armatures one controlled by each electromagnet, a pivoted locking dog having a horizontal arm and a vertical arm and movable between an operative and an inoperative position, a counterweight secured to one end of the horizontal arm of said dog for biasing said dog to its inoperative position, a first resilient strip attached to one said armature and coacting with the horizontal arm of said dog at the end opposite said counterweight for at times moving said dog from its inoperative to its operative position in response to the movement of said one armature away from its associated electromagnet, an interlocking arm attached to the other said armature and provided with an ofiset portion for engaging said vertical arm when said dog occupies its operative position to limit the movement of said other armature away from its associated electromagnet, and a rigid strip attached to said one armature and cooperating with the horizontal arm of said dog at the end opposite said counterweight for at times moving said dog partway toward its inoperative position when said one armature is moved toward its associated electromagnet.

11. An interlocking relay comprising two electromagnets, two armatures one controlled by each electromagnet, a movable locking dog, means attached to one armature for at times moving said dog from a first position to a second position, resilient means attached to said one armature for at times exerting a force on said dog which tends to return it to its first position, and means attached to the other armature and cooperating with said dog for restricting the movement of said other armature when said dog occupies its second position.

12. An interlocking relay comprising two electromagnets, two armatures one controlled by each electromagnet, each said armature being biased by gravity to a first position and being movable from said first position to a second position in response to energization of the associated electromagnet, a movable locking dog, means attached to one armature and eifective when said one armature moves from its second position to its first position for moving said dog from a first position to a second position, means attached to the other armature and cooperating with said dog when said dog is moved to its second position for restricting the movement of said other armature, and resilient means attached to said one armature and effective when said armature is moved from its first position to its second position for exerting a force on said dog which tends to restore said dog to its first position.

13. An interlocking relay comprising two electromagnets, two armatures one controlled by each electromagnet, a movable locking dog, means attached to one armature for at times moving said dog from a first position to a second position, resilient means attached to said one armature for at other times exerting a force on said dog which tends to restore it to its first position, means attached to the other armature for at times moving said dog from its first position to a third position, resilient means attached to said other armature for at other times exerting a force on said dog which tends to restore it to its first position, means attached to said one armature and cooperating with said dog when said dog occupies its third position for restricting the movement of said one armature, and means attached to said other armature and cooperating with said dog when said dog occupies its second position for restricting the movement of said other armature.

14. An interlocking relay comprising a first and a second electromagnet, a first and a'second armature controlled respectively by said first and second electromagnets, each said armature being movable to a picked up or a released position according as the associated electromagnet is energized or deenergized, a pivoted locking dog having a first and a second operating arm and a first and a second holding projection and being movable from an intermediate position to a first or a second extreme position, means for biasing said dog to its intermediate position, means attached to said first armature and cooperating with said first operating arm to rotate said dog from its intermediate position to its first extreme position in response to movement of said first armature from its picked up to its released position, means attached to said second armature and cooperating with said second operating arm to rotate said dog from its intermediate position to its second extreme position in response to movement of said second armature from its picked up to its released position, means attached to said first armature and cooperating with said first holding projection when said dog occupies its second extreme position for restricting the movement of said first armature away from its picked up position, means attached to said second armature and cooperating with said second holding projection when said dog occupies its first extreme position for restricting the movement of said second armature away from its picked up position, a first resilient strip secured to said first armature and cooperating with said first operating arm to exert a force on said dog tending to restore said dog to its intermediate position when and only when said first armature occupies its picked up position and said dog occupies its first extreme position or any position between its intermediate and its first extreme position, and a second resilient strip secured to said second armature and cooperating with said second operating arm to exert a force on said dog tending to restore said dog to its intermediate position when and only when said second armature occupies its picked up position and said dog occupies its second extreme position or any position between its intermediate and its second extreme position.

15. An interlocking relay comprising two armatures one controlled by each electromagnet, two interlocking arms one secured at one end to each of said armatures, each said interlocking arm being provided at its free end with two bifurcations, a pivoted locking dog biased to a first position and provided with two operating arms and with two holding projections, the parts being so proportioned that if one of the armatures becomes released before the other armature, one of the bifurcations on the interlocking arm attached to said one armature will engage one of the operating arms of said dog and rotate said dog from said first position to a second position and that if said other armature becomes released before said one armature, the one bifurcation on the interlocking arm attached to said other armature will engage the other operating arm of said dog and rotate said dog from its first position to a third position, the parts being further so proportioned that if said other armature becomes released while said dog occupies its second position the other bifurcation on the interlocking arm attached to said other armature will move into engagement with one of the holding shoulders on said dog and thus restrict the movement of said other armature and that if said one armature becomes released while said dog occupies its third position the other bifurcation on the interlocking arm attached to said one armature will move into engagement with the other holding shoulder on said dog and restrict the movement of said one armature, and two flexible strips one secured to each of said interlocking arms and each cooperating with one of the operating arms in such manner that if said dog occupies its second position when said one armature is picked up the strip attached to the interlocking arm attached to said one armature will exert a force on said dog tending to restore said dog to its first position and that if said dog occupies its third position when said other armature is picked up the strip attached to the interlocking arm attached to said other armature will exert a force on said dog tending to restore said dog to its first position.

16. An interlocking relay comprising two electromagnets, two armatures one controlled by each electromagnet, a movable locking dog, means attached to one armature f or at times moving said dog from a first position to a. second position and for at other times exerting a force on said dog which tends to return said dog at least part way toward its first position, and means attached to the other armature and cooperating with said dog for restricting the movement of said other armature when said dog occupies its second position.

17. An interlocking relay comprising two electromagnets, two armatures one controlled by each electromagnet, a pivoted locking dog, means for biasing said dog to a. first position, resilient means attached to one armature for at times moving said dog from said first. position to a second position, other means attached to said armature for at other times exerting a force on said dog which tends to move said dog at least part way toward its first position, and means attached to the other armature and cooperating with said dog for restricting the movement of said other armature when said dog occupies its second position.

18. An interlocking relay comprising two electromagnets, two armatures one controlled by each electromagnet, a pivoted locking dog, means for biasing said dog to a first position, resilient means attached to one armature for at times moving said dog from said first position to a second position, other means attached to said other 10 armature for at other times assisting said biasing means in restoring said dog to its first position, and means attached to the other armature and cooperating with said dog for restricting the movement of said other armature when said dog occupies its second position.

19. An interlocking relay comprising two electromagnets, two armatures one controlled by each electromagnet, each said armature being biased by gravity to a first position and being movable from said first position to a second position in response to energization of the associated electromagnet, a movable locking dog, means for biasing said dog to a first position, means attached to one armature and effective when said one armature moves from its second position to its first position for moving said dog from its first position to a second position, means attached to the other armature and cooperating with said dog when said dog is moved to its second position for restricting the movement of said other armature, and means attached to said one armature and effective when said armature is moved from its first position to its second position for exerting a force on said dog which tends to move said dog at least part way toward its first position.

PAUL N. MARTIN. 

